The present invention relates to a dresser for an abrasive grinding wheel and, more particularly, to a dresser having an improved bearing arrangement facilitating replacement of dresser cutter units. The dresser of the present invention facilitates positioning the dresser with respect to an abrasive wheel for rapid dressing of the wheel.
Prior art dressers have generally included a dresser body upon which a cutter unit, including a plurality of sharp metal teeth, is rotatably mounted. The teeth of the cutter unit are relatively hard and, when held against a rotating abrasive wheel, tend to roughen, or dress, the wheel surface.
Various bearing arrangements have been used to mount the cutter unit on the dresser body so that it may rotate freely when held against the abrasive wheel. A sleeve bearing arrangement, while simple to manufacture, is subject to rapid wear. As a consequence a dresser having a pair of hexagonal bearing supports, each such support including a plurality of sleeve bearing holes for receiving the shaft of a cutter unit, was developed. Such a dresser is shown in U.S. Pat. No. 1,382,176, issued June 21, 1921, to Dobson. An improvement of this design is shown in U.S. Pat. No. 2,926,654, issued Mar. 1, 1960, to Johnston. The hexagonal bearing supports of Dobson and Johnston are held in slots on opposite sides of the dresser body and may be removed and reinserted into the body when it is desired to change the sleeve bearing holes in which the cutter unit is mounted. Although providing for improved bearing life over prior art sleeve bearing dresser designs, the sleeve bearings of Dobson and Johnston required frequent changing of the bearing holes being utilized as the holes became worn.
Accordingly many prior art dressers utilized ball bearing support arrangements for mounting the cutter unit. Abrasive grinding wheel dressers having ball bearings for mounting the cutter unit, such as shown in U.S. Pat. No. 1,878,763, issued Sept. 20, 1932, to Dovell et al; U.S. Pat. No. 1,526,496, issued Feb. 17, 1925, to Hohnhorst et al; U.S. Pat. No. 2,742,891, issued Apr. 26, 1956, to Wise; and U.S. Pat. No. 1,805,514, issued May 19, 1931, to DeMattia, all included relatively complex mounting arrangements for holding the ball bearings in place in the body of the dresser. At the minimum, a number of screws would need to be removed from the dresser body in order to remove the bearings and cutter unit and substitute a new cutter unit. Further adjustments might also be required to set the cutter unit end play.
Many grinding wheel dressers are hand held and positioned manually on the grinding wheel tool rest during the dressing operation. In order to facilitate positioning of the dresser with respect to the wheel and to aid the operator in holding the dresser in position during the dressing operation, dressers, such as shown in Dovell et al, supra, include a pair of feet extending laterally from the body of the dresser. The dresser is positioned on the tool rest such that these feet extend over the edge of the rest closest to the grinding wheel. The dresser may then be pivoted about this edge of the tool rest to bring the cutter unit into contact with the grinding wheel, while keeping the teeth of the cutter unit properly aligned with the grinding surface of the wheel. Where the tool rest has become uneven through wear and one of both of the feet are held in contact with an uneven portion of the rest, the dresser may be misaligned with respect to the abrasive grinding wheel.
Other prior art dresser units have been permanently mounted on support structure adjacent the abrasive wheel, such that they may be pivoted into contact with the abrasive grinding wheel during the dressing operation. U.S. Pat. No. 272,615, issued Feb. 20, 1883, to Andrews; U.S. Pat. No. 1,349,452, issued May 11, 1920, to Gorham; and U.S. Pat. No. 1,811,933, issued June 30, 1931, to Hohnhorst et al, all disclose dressers which are permanently mounted adjacent a grinding wheel. Such dresser mounting arrangements have typically hindered the operator in use of the grinding wheel and, therefore, have not been widely used.
Accordingly, there is a need for an improved dresser utilizing ball bearing supports for the cutter unit and permitting the cutter unit to be changed rapidly and simply. Additionally, there is a need for an improved dresser permitting quick and accurate alignment of the cutter unit with respect to the grinding wheel. Also, a need exists for a dresser permanently mounted adjacent an abrasive grinding wheel which will not interfere with the use of the wheel.